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Camelids have been
categorized as induced ovulators and present dogma
suggests that physical stimulation during copulation is
primarily responsible for eliciting ovulation. Recent
discoveries, however, challenge this dogma. The project focuses
on the isolation and characterization of an ovulation-inducing
factor (OIF) present in the seminal plasma of camelids. The
factor was initially reported in Bactrian camels, but has not
been documented in any other species.
Studies were conducted to document
the existence of an OIF in the seminal plasma of alpacas and
llamas. In Experiment 1, female alpacas
were given alpaca seminal plasma or saline
intramuscularly or by intrauterine infusion. Only alpacas that
were given seminal plasma intramuscularly ovulated (93%). In
Experiment 2, ovulation was detected in 90% llamas at a mean of
29 hours after seminal plasma treatment. Plasma progesterone
concentrations were maximal 9 days after treatment and back to
minimum at 12 days after treatment. In Experiment 3, females
were given seminal plasma, GnRH (positive control), or saline
(negative control), and ovulation was detected in 100%, 83% and
0% in the respective groups. Blood samples taken every 15
minutes for 8 hours after treatment revealed that seminal plasma
caused circulating luteinizing hormone (LH) to become elevated
within 1 hour and remain elevated for over 8 hours. Compared to
the GnRH group, the corpus luteum (CL; progesterone-producing
gland in the ovary necessary for maintenance of pregnancy) grew
larger and plasma progesterone concentration was twice as high
in the seminal plasma group. Results show, for the first time,
that a potent ovulation-inducing factor is present in the semen
of alpacas and llamas. Treatment-induced ovulation was
associated with a surge in circulating concentrations of LH and
enhancement of CL form and function.
The existence and nature of
this factor has direct implications on fertility, infertility,
breeding management, and commercial development of therapeutic
drugs for alpacas. The evolutionary conservation of such a
factor raises the possibility of its existence in other induced
and spontaneously ovulating species; hence, the characterization
of OIF in the seminal plasma of alpacas may have much broader
implications. Further studies are being conducted to
isolate and characterize the chemical in semen of alpacas and to
determine if it is present in other species.
Publications as a result of Alpaca Research Foundation
funding:
Adams GP, Ratto MH, Huanca W, Singh
J (2005) Ovulation-inducing factor in the seminal plasma of
alpacas and llamas. Biology of Reproduction 73:452-457.
Ratto MH, Huanca W, Huanca T,
Singh J, Adams
GP
(2004) Ovulation-inducing factor in seminal plasma:
species comparison and molecular weight determination.
Proceedings of the annual meeting of the Society
for the Study of Reproduction, Vancouver, BC
August 2004, Abstract 181.
Adams GP, Ratto MH, Singh J (2004) Ovulation-inducing
factor in the seminal plasma of llamas. International Congress
on Animal Reproduction, Porto Seguro, Brazil August 2004, p 217.
Ratto MH, Huanca W, Singh J, Adams GP. (2005). Effect of
OIF on ovulation rate and luteal development in llamas. 1st
Annual Reproductive Science and Medicine Research Symposium.
March 3, 2005, p 18. (Best basic science paper, 2nd
Place)
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